Examples of display devices which display images include a liquid crystal display device. A liquid crystal display device includes a liquid crystal panel and a light source (backlight). The liquid crystal panel functions as a spatial modulation element. The light source has a planar shape and emits light toward the back side of the liquid crystal panel. Light passing through the liquid crystal panel is spatially modulated so that an image is formed on the liquid crystal panel.
With the aim of achieving images with enhanced presence using such a liquid crystal display device, three dimensional (3D) displays capable of representing 3D images are being developed. A 3D display shows a different image to each of the right and left eyes of a user to cause parallax therebetween so that the user can see a 3D image.
For example, a 3D display system including glasses has been proposed which allows a user wearing glasses having a special optical effect to see 3D images. However, the 3D display system including glasses requires a user to take the trouble to wear the glasses each time the user wants to see a 3D image, which results in poor usability. Thus, in recent years, a glasses-free 3D display has been proposed which allows a user to see 3D images without such glasses.
For example, Patent Literature 1 discloses a glasses-free 3D display including a light guide plate having a special shape and a right light source and a left light source disposed at right and left sides of the light guide plate, respectively. The right and left light source are alternately turned on. When the right light source is on, the light from the right light source enters the light guide plate through the right side, and the light outgoing from the light guide plate converges at the right eye of a user. When the left light source is on, the light from the left light source enters the light guide plate through the left side, and the light outgoing from the light guide plate converges at the left eye of the user. The liquid crystal panel display a right-eye image while the right light source is on and a left-eye image while the left light source is on, so that the user can view a 3D image without using special glasses.
However, the user of the 3D display disclosed in Patent Literature 1 needs to fix the positions of the eyes at predetermined positions to see a 3D image. When the eyes of the user are not at the predetermined positions, the light from the light guide plate cannot converge at the eyes of the user, and therefore the user cannot see a 3D image.
Patent Literature 2 discloses a glasses-less 3D display which is proposed to solve the problem. The 3D display includes a light deflector capable of adjustably deflecting light. The light deflector deflects light by taking advantage of modulation of the refractive index of liquid crystal upon application of voltage, for example. The light deflector deflects incident light in a certain time so that outgoing light converges at the right eye of a user. A liquid crystal panel displays a right-eye image synchronously with the time. In a subsequent time, the light deflector deflects incident light so that outgoing light converges at the left eye of the user. The liquid crystal panel displays a left-eye image synchronously with the subsequent time. The liquid crystal panel alternately displays right-eye images and left-eye images with a predetermined period so that the user can see the images displayed on the liquid crystal panel as 3D images.